@misc{indiciae4b25879b2000,
  title = {Electronic filters, hearing aids and methods},
  author = {Engebretson, A. Maynard and O'Connell, Michael P. and Zheng, Baohua},
  year = {1991},
  url = {https://ntrs.nasa.gov/citations/20080004409},
  note = {Source identifier: 20080004409}
}